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Objective: To assess the cost of congenital heart disease (CHD) and to assess whether practice pattern or price was more responsible for variation. Research Design and Setting: Data were collected from Charleston, NC; Columbus, Ohio; Detroit, Mich; Houston, Tex; Los Angeles, Calif; and New York, NY. The CHD was first classified as to physiologic characteristics and severity. For each type of CHD, the number of clinic visits, hospitalizations, and years of medication use were estimated. Results: On the basis of actual charges, the 'prices' were calculated as follows, in 1992 dollars: for patients from birth to 21 years: benign disease (19% of patients), $3940; acyanotic disease (45%), $49730; cyanotic disease (36%), $102 084; and average for all CHD categories, $59 877; for patients 22 to 40 years of age (of whom 24% had resolved defects or were dead): benign disease (19%), $3470; acyanotic disease (52%), $12981; cyanotic disease (29%), $39 187; and average for all CHD, $18 773. The cost for the group from birth to 21 years varied from $47 500 to $73 600, accounting for 55% by practice (number of echocardiograms and cardiac catheterizations) and 45% by price, although mortality was similar. Conclusions: The treatment of CHD is comparatively inexpensive, especially in adult survivors. The variation in both practice and price bears further study, with comparisons to determine the most cost-effective strategies for treating these patients. (Arch Pediatr Adolesc Med. 1994;148:1039-1045), Treatment costs for congenital heart disease (CHD) seem reasonable, although medical centers appear to vary in their CHD treatment practice patterns and charges. Researchers studied the medical records of CHD patients younger than age 22 and those between 22 and 40. Patients were divided into categories based on the characteristics and severity of their CHD. Medical services used by each category of patients in six different medical centers were estimated to determine the treatment costs of CHD. For patients under age 22, 19% had benign CHD that required medical expenditures of $3,940; 45% had acyanotic disease with treatment costs of $49,730, and 36% had cyanotic CHD with treatment costs of $102,084. For patients between the ages of 22 and 40; 19% had benign disease with treatment costs of $3,470; 52% had acyanotic disease that cost $12,981, and 29% had cyanotic disease that cost $39,187. In CHD patients under age 22, there was a 55% variation in treatment charges between the six medical centers. Variations in practice patterns accounted for 55% of these differences and prices charged for 45%.

Early reports of direct-current catheter ablation (DCCA) of the atrioventricular (AV) junction for resistant AV tachycardias documented efficacy of DCCA with little morbidity. Nine patients underwent DCCA at our institution 4 to 9 years ago: 3 patients had DCCA in the coronary sinus for permanent junctional reciprocating tachycardia, 2 patients had His ablation, 2 had coronary sinus and His ablation for permanent junctional reciprocating tachycardia, and 2 had DCCA for congenital junctional ectopic tachycardia. Shocks (total 1 to 5) ranged from 12.5 to 400 J. Five patients had pacemaker implant at the time of DCCA. During follow-up, 3 patients developed clinical ventricular tachycardia: all 3 had DCCA of the His bundle. One asymptomatic patient with ventricular tachycardia, who had DCCA of the bundle of His, died suddenly 6 years later with ventricular fibrillation. Autopsy revealed 2 ventricular scars: 1 extending from the AV junction and 1 in the outflow tract. No patient with DCCA limited to the coronary sinus developed ventricular tachycardia. DCCA of the His bundle can result in late ventricular arrhythmias, possibly a result of extension of the DCCA lesion into the ventricle. These late findings should be considered in evaluating the safety and efficacy and follow-up for patients undergoing radiofrequency ablation. (Am J Cardiol 1992;70:765-768)

Myocardial infarction (MI), a common occurrence in adults, is generally considered to be rare in children. Electrocardiographic criteria for diagnosis of MI in adults are well known and accepted, but no general criteria exist for children. We report 37 autopsy-proved cases of transmural MI and electrocardiographic evidence of Mi in 30 of these cases. A variety of conditions previously reported to produce 'pseudo-infarction'' are included in these cases of MI, including myocarditis, hypertrophic cardiomyopathy, and the cardiomyopathy of Duchenne's muscular dystrophy. Compilation of the electrocardiographic data in all patients allowed for the development of criteria for this diagnosis of MI in childhood, and include wide Q waves (>3S ms) with or without Q-wave notching, ST-segment elevation (>2 mm), and prolonged QT interval corrected for heart rate (QTc >440 ms) with accompanying Q-wave abnormalities. With use of these electrocardiographic criteria, an additional 3 patients were subsequently diagnosed prospectively with Mi and confirmed on autopsy. Pathologic evaluation confirmed the location of infarction predicted by the electrocardiograms in all 3 cases. (Am J Cardiol 1992;69:1545-1548)

Ventricular arrhythmias in patients after total surgical repair of tetralogy of Fallot have been associated with late sudden death. in this large multicenter retrospective study of 359 patients with postoperative tetralogy of Fallot, spontaneous ventricular premature complexes (VPCs) on 24-hour ambulatory electrocardiographic monitoring and laboratory-induced ventricular tachycardia (VT) by electrophysiologic stimulation were analyzed. The mean age at surgical repair was 5 years and the mean follow-up duration after repair was 7 years. Spontaneous VPCs on ambulatory monitoring were found in 48% and induced VT on electrophysiologic stimulation was found in 17% of patients. Both spontaneous VPCs and induced VT were significantly related to delayed age at repair, longer follow-up interval, symptoms of syncope or presyncope and right ventricular systolic hypertension (>60 mm Hg) (p 8 mm Hg. The VPCs on ambulatory monitoring were more complex with increasing age at repair and follow-up duration. induction of VT on electrophysiologic stimulation correlated with spontaneous VPCs including VT on 24-hour ambulatory electrocardiographic monitoring. The electrophysiologic stimulation protocol varied and the induction of VT increased with a more aggressive stimulation protocol. While induced sustained monomorphic VT was related to all forms of spontaneous VPCs, induced nonsustained polymorphic VT was related to more complex forms of VPCs on ambulatory monitoring. VT was not induced in asymptomatic patients who had normal 24-hour ambulatory electrocardiographic monitoring and normal right ventricular systolic pressure. Late sudden death occurred in 5 patients, most of whom had spontaneous VPCs on ambulatory monitoring and right ventricular diastolic pressure >8 mm Hg, but none had induced VT with a nonaggressive electrophysiologic protocol. (Am J Cardiol 1990;6S:655-661), Tetralogy of Fallot, a congenital malformation of the heart, is repaired surgically, usually with prolonged survival. However, sudden death occurs in as many as 5 percent of these patients, and is attributed to various cardiac arrhythmias (dysfunctional heart rhythms), in particular, ventricular premature complexes (VPC; arrhythmias of the ventricles, the main pumping chambers of the heart). Spontaneous VPCs have resulted following induction of ventricular tachycardia (VT; rapid, ineffectual heartbeat). The relationship of the ability to induce VPCs in patients to occurrence of sudden death was studied in 359 patients; the average age was five years. Patients with right ventricle systolic hypertension had surgical repair at a later age than those with normal pressure. VPCs were present in 48 percent of patients during 24-hour ECG (electrocardiograph) monitoring, and these patients had delayed surgical repair, had a longer follow-up interval between medical checkups, and had more occurrences of syncope (fainting) and right ventricular systolic hypertension. Analysis showed that delayed repair and longer follow-up were significantly related to VPCs. During electrophysiological study, electrical stimulation could induce VT in 60 patients (17 percent), and this was related to delayed repair, increased follow-up interval, syncope, right ventricular systolic hypertension, and VPC. Seven patients died of cardiac causes, of whom five died suddenly. Because this is a small number, no prognostic factors can be identified. However, VPCs during 24-hour ECG and right ventricular systolic hypertension were present in most patients. VT was not induced by mild stimuli in these patients. Further study is needed to follow-up on these findings. (Consumer Summary produced by Reliance Medical Information, Inc.)

The QT interval extends from the beginning of the QRS complex to the end of the T wave. Since the report of Jervell and Lange-Nielsen in 1957, it has been difficult to determine whether to measure a QT or a QU interval. U waves are more prominent in the left chest leads and less prominent in lead II, with the end of the T wave in lead II corresponding to the end of significant repolarization in any other lead. Therefore, by convention, lead II has been chosen to measure the QT interval. Numerous attempts at correction have been made, but Bazett's correction (QT/RR) remains the current standard. In stable sinus rhythm, a QT interval corrected for heart rate ([QT.sub.c]) of >0.44 sec is considered abnormal. In this study, in the presence of sinus arrhythmia, the QT interval following the shortest RR interval was >0.46 sec in 98.4% of patients with the congenital long QT syndrome, but in only 3.8% of control subjects (p 0.03 seconds in a 10-sec rhythm strip of lead II in 33% of long QT syndrome patients but 0% of controls (p Why an entire article on the measurement of the QT interval? the answer is that, if any absolute value for the PR interval or QRS duration were associated with sudden death, there would probably be a report on measurement of these as well. However, since the exact value of the QT interval may be an important predictor of sudden death in certain situations, Its accurate measurement becomes important. The first consideration addressed in this report will be the definition of the QT interval an its measurement during stable sinus rhythm. This will be followed by a discussion of variations in the QT interval with sinus arrhythmia and with day-night changes in autonomic tone, measurement of the QT interval on the Holter, and the feature assessment of repolarization. QT INTERVAL IN STABLE SINUS RHYTHM The QT interval is measured 'from the beginning of depolarization of the QRS complex to the end of the T wave.' This seemingly innocuous definition is fraught with problems. The first of these is whether to include the U wave in the measurement. The following statement from Jervell and Lange-Nielsen[1] provides an apt description: 'The abnormal complexes in these cases were, in our opinion, caused by delayed repolarization of the heart muscle. The question of nomenclature, therefore, seems to be less importance. When making use of the term QT interval, however, we are well aware of the possible merging of T and U waves.' In many leads, a discrete T wave may be followed by a discrete U wave, but in most cases of the long QT syndrome, just as Jervell and Lange-Nielsen described, the T and U waves merge to produce a 'bizarre' shape of the T wave. A significant portion of repolarization is present in the second half of that complex so that the end of the T wave (or T-U wave) may have a higher amplitude than the beginning of the wave. Therefore, the end of repolarization (whether it be T or U) is usually included in the measurement of this interval. The problems of distinguishing between T and U waves are minimized by measuring the QT interval in lead II. The vectors of repolarization are such that in this led there is generally a long single wave rather than 2 discrete T of U waves. Because no data are currently available to indicate which leads to measure, the convention followed by Moss et al[2] has been to use lead II. According to Benhorin et al,[3] the length of the QT interval may vary more in different leads in those with long QT syndrome than it does among normal persons. A study is underway to determine whether measurement of the QT interval in lead II provides appropriate sensitivity and specificity. The final question concerns correction of the QT interval for heart rate. In 1918, Bazett[4] reported correction of the QT interval for heart rate using the square root function. This has become the world standard, with 'abnormal' usually defined as >0.44 sec. There have been numerous challenges to this correction, some of which are detailed elsewhere in this symposium. With so many possibilities for error, it is understandable that computer measurement of the QT interval and the QT interval corrected for heart rate ([QT.sub.c]) may not be accurate in all cases. MEASUREMENT OF THE QT INTERVAL IN SINUS ARRHYTHMIA Any correction of the QT interval generally involves the RR intervals, but how does one measure the QT interval in the presence of a varying RR interval? We recently performed a study measuring the Qt interval and its correction in 143 subjects; 63 of these had shown symptomatic congenital long QT syndrome and 80 were normal controls. A number of different parameters on a 10-sec rhythm strip were measured, including the longest, shortest, and mean QT and RR intervals. We determined that, by measuring the QT following the shortest RR interval, the best cutoff point was 0.46 sec. We found that the [QT.sub.c] (using the Bazett correction) following the shortest RR interval was 0.46 sec in only 3.8% of controls but in 98.4% of those with the long QT syndrome (p In examining the variation of the QT interval itself in lead II, we found that variation in a 10-sec period of QT interval was >0.03 sec in none of the control patients but in 33% of the patients with the long QT syndrome. Therefore, in the presence of sinus arrhythmia, if the QT interval varies by more than 0.03 sec or the longest [QT.sub.c] (following the shortest RR interval) is >0.46 sec, it is highly probable that the patient has the congenital long QT syndrome. QT INTERVAL VARIATION THROUGH 24 HOURS It has been well-demonstrated that sympathetic and parasympathetic tone alter the relation between QT interval and heart rate. As a result, the [QT.sub.c] changes with changes in autonomic tone.[5,6] Browne et al[5] determined that the difference in QT interval between the awake and sleeping states was 19 [ + or -] 7 msec when calculated at a heart rate of 60 beats/min. It was hypothesized that prolongation of the QT interval during sleep could reflect either increased vagal tone or sympathetic withdrawal. Morganroth et al[6] studied 20 normal subjects and found the variability in [QT.sub.c] to be 76 + 19 msec from day to night. They observed that 11 of their subjects had a maximum [QT.sub.c] of >440 msec and 1 had a maximum [QT.sub.c] of >500 msec. This study was performed to address the question of the potential changed in [QT.sub.c] under different circumstances, such as during use of an antiarrhythmic drug. The investigators concluded that a changed in [QT.sub.c] of >75 msec or a maximal [QT.sub.c] of >500 msec was 'abnormal.' Therefore, it is likely that different ranges of 'normal' will need to be developed, depending on the time of day and state of arousal. MEASUREMENT OF THE QT INTERVAL ON HOLTER As Holter assessment of patients for the presence of long QT intervals becomes more common, the question arises as to the correspondence between standards electrocardiogram (ECG) measurement of the QT interval and the Holter measurement. In a recently completed study we measured the same complexes on the standard ECG and on the Holter.[7] Two different observers measured the uncorrected QT interval on 2 leads of a standard Holter and compared them with their corresponding standard ECG leads, using lead V1 (51 observations) and lead V5 (49 observations). For lead V1, the 95% confidence intervals indicated that the Holter measurement could range from 55 msec longer to 100 msec shorter than the standard ECG measurement (mean Holter measurement, 24 msec shorter). In lead V5, the 95% confidence interval of the Holter measurement was 62 msec longer to 42 msec shorter than the standard ECG measurement (mean Holter QT interval, 13 msec longer). The implications of this study are that the QT interval measured on the Holter is very different from that measure using the same complex on the standard ECG. Unfortunately, there is no way to predict, in an individual complex, whether the Holter measurement will be longer or shorter than the standard ECG measurement. The error may be as much as 50-100 msec (i.e., a standard ECG QT measurement of 0.44 sec and a Holter measurement ranging from 0.49 to 0.34 sec). There are a number of possible explanations for these findings. The low-frequency response on the Holter may be limited in order to produce a stable baseline. These limitations in the low-frequency response may cause a negative shift in the ST segment, a negative overshoot of the offset of the T wave, or a decreased amplitude of the T wave. Therefore, Holter studies should probably be compared with other Holter studies rather than with studies using standard ECGs. It is likely that the low-frequency bias will be stable over a 24-hour period and similar from day to day in a given patient using similar Holter recording equipment. This calls into question the practice of using different Holter equipment to measure the QT interval in studies involving groups of patients. THE FUTURE QUANTITATION OF REPOLARIZATION The QT interval is not the ultimate answer to the description of repolarization. As we have seen, there ar numerous problems in interpreting the QT interval because it may change depending on lead selection, heart rate, and autonomic tone. Certain changes in repolarization that might occur during antiarrhythmic drug use may not always be reflected in the measurement of the QT interval. For these reasons, attempts have recently been made to improve the description of ventricular repolarization. Merri et al[8] have developed a computer algorithm to interpret the electrocardiographic repolarization segment and automatically measure 11 variables quantitating these characteristics. A final set of 7 variables was used in the statistical analysis. These variables included such measurements as symmetry of the T wave, area of the T wave, and the interval from the end of the S wave to the maximum amplitude of the T wave. These measurements require automated ECG analysis software that is currently investigational, but which may become available for clinical use is the near future. It is hoped that these newer methods will provide better sensitivity and specificity for detecting the electrophysiologic changes that increase the risk of arrhythmia and sudden death. REFERENCES [1] Jervell A, Lange-Nielsen F. Congenital deaf-mutism, functional heart disease with prolongation of the Q-T interval, and sudden death. Am Heart J 1957;54:59-68. [2] Moss AJ, Schwartz PJ, Crampton RS, Locati E, Carleen E. The long QT syndrome: a prospective international study. Circulation 1985;71:17-21. [3] Benhorin J, Merri M, Alberti M, Locati E, Moss AJ, Hill WJ, Cui L. Long QT syndrome: new electrocardiographic characteristics. Circulation 1990;82:521-527. [4] Bazett HC. An analysis of the time-relations of electrocardiograms. Hear 1918;7:353-370. [5] Browne K, Prystowsky E, Heger JJ, Chilson DA, Zipes DP. Prolongation of the Q-T interval in man during sleep. Am J Cardiol 1983;52:55-59. [6] Morganroth J, Brozovich FV, McDonald JT, Jacobs RA. Variability of the QT measurement in healthy men, with implications for selection of an abnormal QT value to predict drug toxicity and proarrhythmia. Am J Cardiol 1991;67:774-776. [7] Christiansen JL, Guccione P, Garson A. Differences in QT measurement on ambulatory and standard electrocardiography. Proceedings of the Fifth International Congress of Ambulatory MOnitoring, 1992. In press. [8] Merri M, Alberti M, Benhorin J, Hall JW, Locati E, Moss AJ. Electrocardiographic quantitation of ventricular repolarization. Circulation 1989;80:1301-1308. Arthur Garson, Jr, MD, MPH From the Division of Pediatric Cardiology, Duke University Medical Center, Durham, North Carolina.